1. Field of the Invention
The present invention relates to positioning apparatus and more particularly to a base apparatus for adjusting the degree of tilt-swivel and side-to-side displacement of the screen of a cathode ray tube terminal device.
2. Description of the Prior Art
There has been a significant increase in the frequency of use of cathode ray tube (CRT) display terminal devices. Therefore, it becomes more essential to make such devices more convenient and comfortable for an operator to use. One problem encountered by operators concerns the amount and angle of incident light which falls on the screen surface of the CRT display device that produces reflection making it impossible in some instances for an operator to view information being displayed on the screen. Normally, the amount of incident light varies with the time of day and the displacement or positioning of the CRT device on the operator's work surface. In view of this, it becomes very desirable for an operator to be able to alter the viewing angle of the CRT screen's surface by tilting the CRT forward or backward so as to minimize or eliminate reflections.
Some prior art CRT display devices have the tilt mechanism built into the device. That is, the CRT's tube casing or housing is mounted on pivotal support base structures which permit the tube screen to be tilted by the operator. This type of arrangement has been found to introduce additional problems in constructing a suitable plastic housing or casing structure for the CRT device. Also, it becomes difficult to provide a tilt mechanism sturdy enough to meet stringent shock and vibration test requirements.
An alternative mechanism for providing the tilting of CRT screen is found in U.S. Pat. No. 4,368,867 entitled, "Tilt Base for a CRT Display Terminal". This patent discloses a tilt base assembly which includes a base and two pairs of elongated feet which attach to the bottom of the CRT display terminal. The base includes a pair of trapezoidal shapes base members which attach to the ends of a horizontal plate. The elongated feet suspended from the bottom of the terminal unit rests on both inclined surfaces of each trapezoidal shaped base member. The front inclined surfaces of the trapezoidal shaped base members are constructed to include a plurality of indentations which provide a corresponding number of fixed stationery positions for providing different operation viewing angles over a range of adjustment. This system has the disadvantage that the viewing angle is not continuously adjustable but instead is confined to a predetermined number of fixed positions. Further, the adjustment of the viewing angle may result in the raising of the center of gravity of the CRT display terminal and therefore require a certain amount of physical effort if the unit is heavy in order to adjust the viewing angle. In addition, since the trapezoidal base member is not attached to the CRT housing, moving the CRT terminal from one place to another may require several steps of: first lifting the terminal to remove the base, moving the base to the new location and then moving the terminal and placing it on the base.
With the advent of personal computers, it has become commonplace to mount a CRT display terminal on top of a enclosure which contains the computer electronics. These personal computers often have a detached typewriter type keyboard which is used by the operator to enter data and control system operation. For these systems, which have a detachable keyboard, it is often desirable to position the electronics enclosure and the top mounted CRT's display terminal off to one side on a desk and to have the keyboard directly in front of the operator on a desk or held in the operator's lap while it is used. In these situations, in which the electronics enclosure and CRT display is off to one side, it is often desirable to be able to swivel the CRT display relative to the electronics enclosure such that the operator can adjust it for operator viewing convenience. To accommodate this need to be able to swivel the CRT display screen relative to the electronics enclosure, various manufacturers have provided swivel mechanisms. One such mechanism is disclosed in U.S. Pat. No. Des. 253,594 entitled, "Combined Turn and Tilt Base". This mechanism provides for both the swivel and tilting of CRT display terminals relative to the electronics enclosure.
Other arrangements are known in the prior art. For example, it is known to use a gimbal mechanism in which the CRT is held by a U-shaped yoke which contains horizontal pins at each upper end of the yoke which support the CRT display and around which the CRT display may be pivoted to provide forward and backward tilt adjustment. The lower end of the yoke is pivotally mounted such that it may be rotated around a vertical axis and thereby allow the unit to be swiveled for operator viewing convenience. Unfortunately, this gimbal mechanism is relatively expensive to construct and often requires some sort of locking device in order to be able to hold the CRT terminal in the desired position. Further, depending upon the weight of the CRT display terminal, the CRT display housing may have to be reinforced around the pivot point to accommodate the relatively large amount of stress that is concentrated in a relatively small area. This type of yoke arrangement has the further disadvantage that different size yoke are needed to accommodate different size CRT display housings.
Another prior art design which provides for both the tilt and swivel of a CRT display unit is found in U.S. Pat. No. 3,970,792 entitled, "Adjustable Mounting Structure for Video Telephone Unit". This patent discloses a rocker member which is inserted within a rectangular socket in a turntable member having a circular periphery which is in turn inserted within a recess within a pedestal. The rocker member is attached to the bottom of the CRT display device and provides for the forward and backward tilting of the CRT display screen. The swiveling of the CRT display is provided by rotating the turntable member relative to the pedestal. In this design, the pedestal remains stationery with respect to the horizontal surface on which it is resting.
Another feature that is desirable with respect to a CRT display terminal that is mounted on top of an electronics enclosure such as that found in personal computers, is the ability to move the CRT display terminal toward one of the other edges of the electronics enclosure depending upon whether the unit is to the right or the left of the operator. This is desirable because the electronics enclosure is usually wider than the CRT display terminal and by moving the CRT display terminal toward either the right or left edge, the operator would be able to position the display terminal as close as possible to himself while still having the CRT display remain on top of the enclosure.
Therefore, what is desirable is to provide a base support mechanism which permit the adjustment of the CRT screen viewing angle by tilting the display forward or backward, swiveling the display around a vertical axis and the side-to-side displacement of the display terminal relative to the viewer.